report previous column

[pprinothsocrep]

I have a report (matrix) with following data

Column (season, NOT date format)

Row (product)

Value (turnover)

               spring summer autumn winter spring+1 summer+1

apples      100    100       200       120     60          80

mangos    100    150       200       240     30          60

I am looking to add colums after each existing column to calculate difference beetween the column and the column before

Result should be like

apples 100 - 100/0% - 200/+100% - 120/-40% - 60/-50% - 80/+33%

mangos 100 - 150/+50% - 200/+33,3% - and so on

First difference cannot be calculated as now previous value

Again : the season column is NOT IN DATE FORMAT